In vivo gene transfer of pigment epithelium-derived factor inhibits tumor growth in syngeneic murine models of thoracic malignancies.

OBJECTIVE: Pigment epithelium-derived factor is known to be an inhibitor of angiogenesis. We hypothesized that in vivo gene transfer of pigment epithelium-derived factor may inhibit tumor angiogenesis and growth in syngeneic models of thoracic malignancies.
METHODS: An adenovirus vector encoding the human pigment epithelium-derived factor cDNA (AdPEDF) was used to transduce human lung cancer cells in vitro. Transgene expression was assessed using Western analysis. Three different murine flank tumors (2 lung, 1 colon) were then established in syngeneic mice and treated intratumorally with phosphate-buffered saline, AdPEDF, or an empty vector (AdNull). Endpoints measured included transgene expression, tumor size, and animal survival, as well as microvessel density within the tumor. Additionally, a murine pulmonary metastasis model was established by intravenous injection of a syngeneic colon adenocarcinoma cell line expressing a marker gene (beta-galactosidase). One day later, treatment (phosphate-buffered saline, AdNull, or AdPEDF) was administered intrapleurally. Tumor burden (gross and histologic inspection, lung weight, and beta-galactosidase expression) was then evaluated 13 days after vector dosing, and survival was recorded.
RESULTS: AdPEDF-derived expression of pigment epithelium-derived factor was demonstrated in vitro and in vivo. In syngeneic murine lung cancer flank tumors, intratumoral administration of AdPEDF significantly inhibited tumor growth (P <.01), prolonged mouse survival (P <.01), and decreased microvessel density (P <.01) compared with control groups. In the pulmonary metastasis model, AdPEDF-treated mice exhibited significantly reduced lung lesions, lung weight (P <.0005), beta-galactosidase expression (P <.05), and animal survival was prolonged (P <.05).
CONCLUSION: Gene transfer of pigment epithelium-derived factor suppresses tumor vascularization and growth, while prolonging survival in syngeneic murine models of thoracic malignancies.